Reduktive Dehalogenierung von Chlorkohlenwasserstoffen während der anaeroben Stabilisierung von Hausmüll

Reductive Dehalogenation of Chlorinated Hydrocarbons during Anaerobic Stabilization of Municipal Wastes During sequential anaerobic digestion of municipal wastes, distinct biogeochemical phases exist which show different capabilities to transform halogenated hydrocarbons. Chlorophenols, tetrachloroethylene, and chloroanilines codisposed together with organic-rich waste substrates are reductively dehalogenated during methanogenic conditions. Lindane is degraded during acidogenesis as well as during methanogenesis. However, degradation in methanogenic leachates is faster by a factor of 10. The poor transformation potential during acidogenesis compared to subsequent transient methanogenic and stabile methanogenic phases cannot be explained by inadequate acclimation of prevailing microorganisms to the codisposed organochlorines. Thus, observed transformation capabilities are a pertinent feature of methanogenic leachates, probably due to prevailing low redox potential and/or presence of suitable microbial activities (not necessarily methanogenis). Dehalogenation of 2,3,4,6-tetrachlorophenol as a model compound is hampered in methanogenic leachate by addition of a surplus of sulfate and is completely suppressed by addition of molybdate which selectively inhibits sulfate reducing microorganisms. Competition for common electron donators (e.g. H₂) is discussed as an explanation of these results. The results point to sulfate reducing microorganisms being involved in reductive dehalogenation of chlorophenols.     

氧化还原条件对红枫湖沉积物磷释放影响的微尺度分析

选取贵州红枫湖为研究对象,在实验室条件下模拟了自然、好氧和厌氧条件下沉积物内源磷的释放过程,联合应用微电极技术和沉积物磷形态分析对沉积物—水界面开展了微尺度观测与研究.结果表明,厌氧条件下红枫湖沉积物总磷含量显著降低,且主要是NaOH提取态磷(NaOH-P)和残渣态磷(rest-P)含量降低所致,厌氧条件下沉积物孔隙水中磷酸盐浓度明显升高,而好氧条件下沉积物孔隙水磷酸盐浓度显著降低,反映厌氧条件显著促进了红枫湖沉积物磷释放.厌氧条件下沉积物内部溶解氧浓度下降、硫还原活动增强可能是导致NaOH-P释放的主要原因.O_2浓度的降低加速了沉积物还原作用并产生大量H2S,进而与二价铁离子形成硫化亚铁沉淀,最终导致NaOH-P(Fe-P)释放到孔隙水中.好氧条件向厌氧条件的转换可通过改变沉积物内部pH值分布和微生物活动促使rest-P释放:厌氧条件下,厌氧微生物不仅可以消耗硫酸根产生H_2S,导致pH值降低,还可消耗有机质,将有机磷转变为无机磷.上述研究结果表明,沉积物—水界面氧化还原环境可影响沉积物氧渗透深度、pH值分布、微生物活动、硫循环以及有机质降解过程,进而控制沉积物磷的形态转化与释放.联合应用微电极技术和沉积物磷形态分析对湖泊沉积物—水界面开展微尺度观测研究是揭示沉积物内源磷释放机制与控制因素的有效途径.     

Flow cytometry and conventional enumeration of microorganisms in ships' ballast water and marine samples

Conventional methods for bacteriological testing of water quality take long periods of time to complete. This makes them inappropriate for a shipping industry that is attempting to comply with the International Maritime Organization's anticipated regulations for ballast water discharge. Flow cytometry for the analysis of marine and ship's ballast water is a comparatively fast and accurate method. Compared to a 5% standard error for flow cytometry analysis the standard methods of culturing and epifluorescence analysis have errors of 2-58% and 10-30%, respectively. Also, unlike culturing methods, flow cytometry is capable of detecting both non-viable and viable but non-culturable microorganisms which can still pose health risks. The great variability in both cell concentrations and microbial content for the samples tested is an indication of the difficulties facing microbial monitoring programmes. The concentration of microorganisms in the ballast tank was generally lower than in local seawater. The proportion of aerobic, microaerophilic, and facultative anaerobic microorganisms present appeared to be influenced by conditions in the ballast tank. The gradual creation of anaerobic conditions in a ballast tank could lead to the accumulation of facultative anaerobic microorganisms, which might represent a potential source of pathogenic species.     

Climate tipping-point potential and paradoxical production of methane in a changing ocean

The global warming potential of methane (CH₄) is about 30 times stronger than that of carbon dioxide (CO₂) over a century timescale. Methane emission is hypothesized to have contributed to global climate change events and mass extinctions during Earth’s history. Therefore, the study of CH₄ production processes is critically important to the understanding of global climate change. It has been a dogma that biogenic CH₄ detectable in the oceans originates exclusively from the anaerobic metabolic activity of methanogenic archaea in hypoxic and anoxic environments, despite reports that many oxic surface and near-surface waters of the world’s oceans are CH₄-supersaturated, thereby rendering net sea-to-air emissions of CH₄. The phenomenon of CH₄ production in oxic marine waters is referred to as the “ocean methane paradox”. Although still not totally resolved, recent studies have generated several hypotheses regarding the sources of CH₄ production in oxic seawater. This review will summarize our current understanding of the importance of CH₄ in the global climate and analyze the biological processes and their underpinning mechanisms that lead to the production of CH₄ in oxic seawater environments. We will also tentatively explore the relationships of these microbial metabolic processes with global changes in climate and environment.     

Effect of Biofuels on Biodegradation of Benzene and Toluene at Gasoline Spill Sites

The risk that benzene and toluene from spills of gasoline will impact drinking water wells is largely controlled by the natural anaerobic biodegradation of benzene and toluene. Benzene and toluene, as well as ethanol and other biofuels, are degraded under anaerobic conditions to the same pool of degradation products. Biodegradation of biofuels may produce concentrations of degradation products that make the thermodynamics for degradation of benzene and toluene infeasible under methanogenic conditions and produce larger plumes of benzene and toluene. This study evaluated the concentrations of fuel alcohols that are necessary to inhibit the anaerobic degradation of benzene and toluene under methanogenic conditions. At two ethanol spill sites, concentrations of ethanol greater ≥42 mg/L inhibited the anaerobic degradation of toluene. The pH and concentrations of acetate, dissolved inorganic carbon, and molecular hydrogen were used to calculate the Gibbs free energy for the biodegradation of toluene. In general, the anaerobic biodegradation of toluene was not thermodynamically feasible in water with ≥42 mg/L ethanol. In a microcosm study, when the concentrations of ethanol were ≥14 mg/L or the concentrations of n‐butanol were ≥16 mg/L, the biodegradation of the alcohols consistently produced concentrations of hydrogen, dissolved inorganic carbon, and acetate that would preclude natural anaerobic biodegradation of benzene and toluene by syntrophic organisms. In contrast, iso‐butanol and n‐propanol only occasionally produced conditions that would preclude the biodegradation of benzene and toluene.     

Enhancing the Performance of Anaerobic Digestion of Dairy Manure through Phase‐Separation

Anaerobic digestion (AD) is an effective way to convert animal manures into profitable by‐products while simultaneously reducing the pollution of water, air, and soil caused by these wastes. Conventional high‐rate anaerobic reactors cannot effectively process animal manures with high solids‐containing wastes. The two‐phase configuration for AD has several advantages over conventional one‐phase processes, e. g., increased stability of the process, smaller size and cost efficient process configurations. In the present study, the experiments were carried out in a two‐phase system composed of an acidogenic reactor and a methanogenic reactor, and in a one‐phase system composed of only a methanogenic reactor. The reactors were operated as unmixed (without an external mixing aid), unsophisticated, and daily‐fed mode. It was found that the two‐phase configuration was more efficient than the one‐phase system. The biogas production in the two‐phase system at a hydraulic retention time (HRT) of 8.6 days (only methanogenic phase) was calculated to be 42% higher at an organic loading rate (OLR) of 3.5 g VS/L·day than that of the one‐phase with a HRT of 20 days. This translates into significant performance improvement and reduced volume requirement. This finding represents a further step in the achievement of wider use of simple anaerobic reactor configurations for waste treatment in rural areas.     

The Influence of the Concentration of Dissolved Oxygen on the Determination of the Dehydrogenase Activity of Activated Sludge Using the Method of TTC Test

Due to its oxidation-reduction potential, oxygen occurs in the TTC test for the determination of the dehydrogenase activity as a competitive hydrogen acceptor. At different oxygen concentrations in the solution to be tested and also at varying rates of oxygen depletion, e.g. in activated sludge samples, thus the formazan formation from TTC shows differences. Under similar anaerobic conditions, the test results of the dehydrogenase activity are higher in most cases and show a smaller range of variation than under aerobic conditions. The importance of the oxygen concentration is demonstrated in investigations with activated sludge, anaerobic conditions being set by addition of Na₂SO₃.     

The Effect of Oxygen on Anaerobic Color Removal of Azo Dye in a Sequencing Batch Reactor

In this study, various amounts of oxygen were added to the anaerobic phase of an anaerobic‐aerobic sequencing batch reactor (SBR) receiving azo dye remazol brilliant violet 5R to mimic the input of oxygen into the anaerobic zones of biological textile wastewater treatment plants. The effect of oxygen on the anaerobic biodegradative capability of the mixed microbial culture for remazol brilliant violet 5R was investigated. To investigate the effect of oxygen on anaerobic azo dye biodegradation, the anaerobic phase of the SBR cultures were exposed to a very low limited amount of oxygen for various air flow rates. Initially, an air flow rate of 20 mL/min was applied, further on the air flow rate in the anaerobic phase was increased up to 40 mL/min. System performance was determined by monitoring chemical oxygen demand, color removal rate, activities of anaerobic (azo reductase) and aerobic enzymes (catechol 2,3‐dioxygenase, catechol 1,2‐dioxygenase). The results of percentage COD reduction at each stage were similar for all runs, giving an overall reduction of 96%. Anaerobic color removal efficiency and azo reductase activity of anaerobic microorganisms were adversely affected by the addition of oxygen. Color removal efficiencies of the anaerobic phases decreased from 80% down to 42 and 38% for the limited oxygen conditions of 20 mL/min and 40 mL/min, respectively. It was observed that the activity of catechol 2,3‐dioxygenase and catechol 1,2‐dioxygenase, involved in breakage of aromatic rings, increased after they are exposed to oxygen limited conditions compared to fully anaerobic conditions. It was also observed that catechol 1,2‐dioxygenase enzyme activity increased by increasing the oxygen level on oxygen limited conditions in the anaerobic zone.     

内陆水体好氧甲烷氧化过程研究进展

内陆水体是全球碳循环的关键组成部分,是大气中甲烷(CH_4)的重要来源,每年从内陆淡水与自然湿地排放进入大气的CH4约为185～357 Tg/a.通常,内陆水体中CH_4主要由分布于水层底部的厌氧区或沉积层内的产甲烷菌介导产生,其向水层表面传输的过程中易被甲烷氧化菌所氧化.甲烷氧化菌可分为好氧甲烷氧化菌和厌氧甲烷氧化菌,有氧条件下,由好氧甲烷氧化菌介导的好氧甲烷氧化过程是水体中甲烷氧化过程的主要形式,湖泊底部产生的CH_4总量中约有99%可以被上覆水体中的好氧甲烷氧化过程所消耗.本文收集文献综合分析阐明,好氧甲烷氧化过程是由水环境因子、水文条件以及不同内陆水体的生态系统特征共同调控,同时也表现在了好氧甲烷氧化菌的生境偏好上.复杂的调控过程构建了内陆水体向大气输送CH_4的动态平衡,并最终反映在内陆水体对全球CH_4循环、碳循环作出的贡献上.     

Relationship between structures of substituted indolic compounds and their degradation by marine anaerobic microorganisms

Degradation of selected indolic compounds including indole, 1-methylindole, 2-methylindole, and 3-methylindole was assessed under methanogenic and sulfate-reducing conditions using the serum-bottle anaerobic technique and marine sediment from Victoria Harbour, Hong Kong as an inoculum. Our results showed that indole degradation was achieved in 28 days by a methanogenic consortium and 35 days by a sulfate-reducing consortium. During degradation under both conditions, two intermediates were isolated, purified and identified as oxindole and isatin (indole-2,3-dione) suggesting that both methanogenic and sulfate-reducing bacteria use an identical degradation pathway. Degradation processes followed two steps of oxidation accomplished by hydroxylation and then dehydrogenation at 2- and then 3-position sequentially prior to the cleavage of the pyrrole ring between 2- and 3-positions. However, none of 1-methylindole or 2-methylindole was degraded under any conditions. 3-Methylindole (3-methyl-1H-indole, skatole) was transformed under methanogenic conditions and mineralized only under sulfate-reducing conditions. It is clear that methyl substitution on 1- or 2-position inhibits the initial attack by hydroxylation enzymes making them more persistent in the environment and posing longer toxic impact.     

Degree of Sulfate‐Reducing Activities on COD Removal in Various Reactor Configurations in Anaerobic Glucose and Acetate‐fed Reactors

Sulfate‐reduction data from various anaerobic reactor configurations, e. g., upflow anaerobic sludge blanket reactor (UASBR), completely stirred tank reactor (CSTR), and batch reactor (BR) with synthetic wastewaters, having glucose and acetate as the substrates and different levels of sulfate, were evaluated to determine the level of sulfate‐reducing activity by sulfate‐reducing bacteria coupled to organic matter removal. Anaerobic reactors were observed for the degree of competition between sulfate‐reducing sulfidogens and methane producing bacteria during the degradation of glucose and acetate. Low sulfate‐reducing activity was obtained with a maximum of 20% of organic matter degradation with glucose‐fed upflow anaerobic sludge bed reactors (UASBRs), while a minimum of 2% was observed with acetate‐fed batch reactors. The highest sulfate removal performance (72–89%) was obtained from glucose fed‐UASB reactors, with the best results observed with increasing COD/SO₄ ratios. UASB reactors produced the highest level of sulfidogenic activity, with the highest sulfate removal and without a performance loss. Hence, this was shown to be the optimum reactor configuration. Dissolved sulfide produced as a result of sulfate reduction reached 325 mg/L and 390 mg/L in CST and UASB reactors, respectively, and these levels were tolerated. The sulfate removal rate was higher at lower COD/SO₄ ratios, but the degree of sulfate removal improved with increasing COD/SO₄ ratios.     

Quality of Water in the Stabilization System from the Point of View Human Medicine

The microbiological quality of water was studied in three parts of the stabilization system for the purification and utilization of dairy effluents (SVOBODA and KOUBEK). Results of three years of investigations dealing with the indicators of general, fecal and virus pollution by selected physiological groups of microorganisms, anaerobic microbes, some facultative pathogenic microorganisms and other selected groups of microorganisms are presented. The conclusions indicate that water discharged into the receiving river is microbiologically safe.     

Using DNA‐Stable Isotope Probing to Identify MTBE‐ and TBA‐Degrading Microorganisms in Contaminated Groundwater

Although the anaerobic biodegradation of methyl tert‐butyl ether (MTBE) and tert‐butyl alcohol (TBA) has been documented in the laboratory and the field, knowledge of the microorganisms and mechanisms involved is still lacking. In this study, DNA‐stable isotope probing (SIP) was used to identify microorganisms involved in anaerobic fuel oxygenate biodegradation in a sulfate‐reducing MTBE and TBA plume. Microorganisms were collected in the field using Bio‐Sep® beads amended with ¹³C₅‐MTBE, ¹³C₁‐MTBE (only methoxy carbon labeled), or ¹³C₄‐TBA. ¹³C‐DNA and ¹²C‐DNA extracted from the Bio‐Sep beads were cloned and 16S rRNA gene sequences were used to identify the indigenous microorganisms involved in degrading the methoxy group of MTBE and the tert‐butyl group of MTBE and TBA. Results indicated that microorganisms were actively degrading ¹³C‐labeled MTBE and TBA in situ and the ¹³C was incorporated into their DNA. Several sequences related to known MTBE‐ and TBA‐degraders in the Burkholderiales and the Sphingomonadales orders were detected in all three ¹³C clone libraries and were likely to be primary degraders at the site. Sequences related to sulfate‐reducing bacteria and iron‐reducers, such as Geobacter and Geothrix, were only detected in the clone libraries where MTBE and TBA were fully labeled with ¹³C, suggesting that they were involved in processing carbon from the tert‐butyl group. Sequences similar to the Pseudomonas genus predominated in the clone library where only the methoxy carbon of MTBE was labeled with ¹³C. It is likely that members of this genus were secondary degraders cross‐feeding on ¹³C‐labeled metabolites such as acetate.     

贵州草海喀斯特高原湖泊湿地甲烷氧化菌群落特征及功能探析

草海是由喀斯特盆地积水发育而形成的一个完整的、典型的高原湖泊湿地生态系统,同时也是中国面积最大的岩溶构造湖.甲烷氧化菌作为一类能够将甲烷氧化为CO₂和水的独特微生物,其活动与生态系统中能量流动和元素循环的关键步骤密不可分.为了解贵州草海喀斯特高原湖泊湿地中甲烷氧化菌的群落结构特征及功能,利用宏基因组技术对浅水沼泽、莎草湿地、深水沉积物进行研究.结果表明,草海湿地中主要的好氧甲烷氧化菌为Methylobacter和Methylomonas,主要的厌氧甲烷氧化菌为Candidatus_Methylomirabilis_oxyfera,属于NC10门的反硝化型厌氧甲烷氧化菌.所研究的4种代谢功能基因种类多样性表现为碳代谢＞氮代谢＞硫代谢＞甲烷代谢;基于KEGG数据库共注释到6大类功能和18条与碳、甲烷、氮、硫相关的完整代谢路径.PCoA分析表明浅水沼泽和莎草湿地中甲烷氧化菌的种类和功能相似,且与深水沉积物存在差异.物种与功能相关性网络分析结果显示Methylacidiphilum_fumariolicum和Methylacidiphilum_kamchatkense与草海湖泊湿地中的各个代谢功能均具有较强的相关性.显著影响草海湿地中大多数甲烷氧化菌的群落结构的环境因素是硝酸盐、电导率、总磷和有机质.     

The Role of Microorganisms in Uranium Behavior in the Water–Rock System

Geochemical processes involving redox reactions and leading to either formation or transformation of geochemical barriers may be largely induced or enhanced by microbial activity. The microbial reduction of uranium is studied as a strategy for rehabilitation of uranium-containing groundwater. The bioremediation mechanism converts dissolved uranium(VI) into low-solubility U(IV). The processes involving dissimilatory reducing bacteria, which facilitate the reduction and retention of U(VI) in soils and rocks, are considered. The diversity of microorganisms involved in anaerobic reduction of uranium is shown. The geochemical conditions that may affect the rate of microbial reduction of U(VI) are specified, i.e., the presence of nitrate ions, phosphate ions, calcium ions, and iron oxides. The mechanisms of their action are examined. Geochemical barriers with the participation of microorganisms are proposed for the rehabilitation of groundwater with uranium removed from groundwater and deposited locally as a result of microbial reduction of U(VI).     

湖库温跃层溶解氧最小值的形成原因、衍生的生态风险及控制研究进展

溶解氧（DO）对湖库的生物地球化学循环、生态系统结构和功能起着至关重要的作用,也是评价水生态系统的敏感性指标.DO浓度的降低对水生态有着重要影响.结果显示,多数湖库在夏秋季热分层期间,由于温跃层较高的密度梯度、藻类衰亡和有机质的降解以及微生物的呼吸作用会消耗大量的DO,从而形成温跃层溶解氧最小值（MOM）,甚至在该区域诱发厌氧状态.MOM可驱动浮游动物日夜垂向迁移,影响无脊椎动物和鱼类分布迁移模式及种群结构,破坏水体生态分布,致使生物非正常死亡,危害水体生态安全;此外,MOM也可诱发温跃层温室气体（CH₄和CO₂）大量形成,影响水源地水质,成为湖库生态安全隐患.目前对MOM所导致的生态风险和水质问题以及最终的控制方法已有较多研究成果,但缺乏综述性的研究.本文从MOM研究历史、研究方法、形成原因、生态风险及控制方法等方面进行论述,并展望今后研究热点,旨在推进MOM的相关研究进展,保障湖库生态平衡和供水水质安全.     

Microcosm Assessment of Polaromonas sp. JS666 as a Bioaugmentation Agent for Degradation of cis-1,2-dichloroethene in Aerobic,Subsurface Environments

Chlorinated ethenes such as tetrachloroethene and trichloroethene have been widely used as dry-cleaning and degreasing solvents. Under anaerobic conditions, microorganisms reduce these parent compounds to less-chlorinated daughter products such as cis-1,2-dichloroethene (cDCE), and often further to ethene. This process can be stalled at cDCE, due to insufficient supply of reductants and/or inadequate microbial-community composition. Recently, a novel bacterium, Polaromonas sp. JS666, was isolated that is able to aerobically oxidize cDCE as sole carbon and energy source. As such, it is a promising candidate for use as a subsurface, bioaugmentation agent at sites where anaerobic bioremediation is inappropriate or has stalled and cDCE has migrated to, and accumulated within, aerobic zones, or where it is practical to impose aerobic conditions. Subsurface sediments or groundwater from six such cDCE-contaminated sites were used to construct microcosms. In every sediment or groundwater inoculated with JS666, the organism was able to degrade cDCE, provided that the pH remained circum-neutral. Even when JS666 was challenged with an alternate carbon source, or in the presence of competitive/predatory microorganisms, there was a measure of success. Collectively, these microcosm studies suggest that JS666 is a viable candidate for the bioaugmentation of aerobic, cDCE-contaminated sites. A minimum inoculation level in excess of 10⁵ cells per mL is recommended for field applications. At this level of inoculation, 100 L of inoculum culture grown to an OD600 of 1.0 should be able to treat a 10-m × 30-m × 80-m (24,000-m³) plot.     

Determination of EC50 Values for Cu,Zn, and Cr on Microorganisms Activity in a Mediterranean Sandy Soil

Ecotoxicity of three potentially toxic metals (PTM) (Cu, Zn, and Cr) in a slightly acidic sandy soil is tested using the soil respiration test (OECD‐217) in order to determine EC₅₀ values for the carbon transformation activity of microorganisms. Addition of an organic amendment of Populus leaves is also crossed with metal spiking in order to investigate possible interaction with metal toxicity. Soil respiration is measured at day 1 and 28 after the soil spiking with the PTM to assess short‐term effects on soil microbial activity. Of the three metals tested, Cu shows the highest toxicity at the longest exposure times (day 28) and Zn shows a strong inhibitory effect in the short‐term (day 1), even though later toxicity diminish significantly. Cr is the least toxic studied PTM. Organic amendment outweighs any adverse effects of these metals, increasing soil respiration, even in the treatments with high doses of metals.     

Dimethylsulfoxidreduktase-Aktivität Charakterisierung der mikrobiellen Biomasseaktivität im Schlamm einer belüfteten Abwasserteichanlage

Dimethyl Sulfoxide Reduction Method for the Characterization of Biomass Activity in Sludge of an Aerated Lagoon The microbial biomass activity was studied in sludge from a wastewater lagoon (Hatzbachtal) which consisted of 4 aerated ponds and one polishing pond. The lagoon was characterized by low BOD₅ loading and high dilution because of water from the surroundings. Sludge samples were taken from 4 sampling sites of each aerated pond and from one site of the polishing pond. The biomass activity in the sludge samples was analysed with the help of dimethyl sulfoxide reductase (DRA) and dehydrogenase (DHA) activity. In addition, C_org-content was also determined. The effect of different reaction parameters on the DRA was studied in relation to incubation period, temperature and atmosphere as well as sludge weight and pH value. The results presented here show that a linear increase in the DRA occured for the sludge weight ranging from 0.1 to 0.5 g, incubation period from 0.5 to 11 h and incubation temperature from 20 to 50 °C. The pH spectrum from acidic to neutral did not effect the DMS formation in sludge. Although the values for DRA were always higher in anaerobic incubation of sludge than in aerobic incubation, the courses of the DRA in both conditions were parallel. Comparing the biomass activity in sludge from different sampling sites of the aerated ponds, the average C_org-content was found to be reflected by the DRA and DHA. Further, the variation in the DRA could represent also the influence of oxygen concentration. Therefore, a reduction in biomass activities indicated a decline in the availability of oxygen.